Indianapolis police say two officers have been slightly injured and seven protesters arrested after demonstrators threw rocks during a march in opposition to the election of Donald Trump. Police Chief Troy Riggs told a news briefing that most of the hundreds of protesters marched peacefully in downtown Indianapolis for several hours on Saturday but a small group became more aggressive later in the evening.

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Police spokesman Major Richard Riddle says some of the group began threatening officers, including chants of “Kill the Police.” They began throwing rocks at officers and police moved in and arrested them.

Riggs says that of seven arrests, four were from Indianapolis and three from out of town.

Police suspect that some instigators arrived from other cities and tried to cause a riot. He praised police for their patience during the demonstration, saying that were trying to allow a peaceful protest. Police say they did use pepper balls at one point during the confrontation.

The police officers who were injured may not even need to go to the hospital to be checked out, Riggs said.